Introduction CSC 440: Software Engineering Slide #1 Topics 1. What is Software Engineering? 2. Software Engineering Life Cycles 3. The Waterfall Model 4. The Unified Process (UP) 5. Object-Oriented Analysis and Design CSC 440: Software Engineering Slide #2 What is Software Engineering? An engineering discipline concerned with all aspects of the software development process Specification Design Implementation Testing Deployment Maintenance CSC 440: Software Engineering Slide #3 Participants in Software Development CUSTOMER Sponsors system development $$$, DEVELOPER needs USER Contractual Uses obligation Builds system system Needs Software system CSC 440: Software Engineering Slide #4 Why Software Engineering? Writing a program is easy Developing a software product is hard CSC 440: Software Engineering Slide #5 Software—A Risky Business •All based on Not waterfall lifecycle. Compl eted •53% cost almost 30% 200% of original estimate. •Estimated $81 Compl eted billion spent on 70% failed U.S. projects in 1995. Source: Standish Report, 1994 CSC 440: Software Engineering Slide #6 Software Life Cycles Waterfall Model Early model of software engineering derived from hardware manufacturing Each stage produces a product, which is consumed by next stage No going backwards Unified Process Iterative model, permitting feedback from later steps of an iteration to earlier steps of the next iteration CSC 440: Software Engineering Slide #7 Why do we need a process? People are more important than any process. Good people with a good process will outperform good people with no process every time. -- Grady Booch CSC 440: Software Engineering Slide #8 Waterfall Model Requirements Design Coding Testing Maintenance CSC 440: Software Engineering Slide #9 Waterfall Model 1. Requirements Eliciting product features needed by customer and encoding them in a precise format 2. Design Creating a solution for the problem defined in the Requirements process 3. Coding Implementing the design as a software product 4. Testing Verifying the correctness of the implementation 5. Maintenance Fixing bugs and adapting the product to new requirements CSC 440: Software Engineering Slide #10 Impact of Risks 100 80 60 40 20 Relative Impact Confronted of Impact Risks Relative CSC 440: Software Engineering Slide #11 Waterfall Model Problems Faulty Assumptions Requirements can be fairly accurate Requirements are stable Design can be done before coding Large steps No feedback Heavy process Many artifacts created to rigidly predict and control software development in a bureaucratic environment CSC 440: Software Engineering Slide #12 Solutions Iterative and incremental development Small steps Feedback and adaptation Progressive refinement and enlargement Early models V Model Boehm’s Spiral Model Agile process Lightweight, adaptive development process that creates only artifacts necessary for the project Based on principles of the Agile Manifesto Examples: UP, XP, SCRUM CSC 440: Software Engineering Slide #13 Feedback and Adaptation Early iterations are farther from the "true path" of the system. Via feedback and In late iterations, a significant change in adaptation, the system converges towards requirements is rare, but can occur. Such the most appropriate requirements and late changes may give an organization a design. competitive business advantage. one iteration of design, implement, integrate, and test CSC 440: Software Engineering Slide #14 The Unified Process Iterative and incremental development process Each iteration includes requirements, design, implementation, and test activities Each iteration produces a working partial system Customer feedback on partial system alter requirements, so final system meets customer needs Iterations are timeboxed: 2-8 weeks Address high risk aspects in early iterations Created by Rational Software (now IBM) CSC 440: Software Engineering Slide #15 UP Iterations Requirements Requirements Feedback from iteration N leads to Design Design refinement and Time adaptation of the Implementation & Implementation & requirements and Test & Integration Test & Integration design in iteration & More Design & More Design N+1. Final Integration Final Integration & System Test & System Test 4 weeks (for example) Iterations are fixed in The system grows length, or timeboxed. incrementally. CSC 440: Software Engineering Slide #16 UP Schedule and Phases Schedule organized into 4 phases Each phase consists of one or more iterations Phases different from Waterfall Model Phases UP Phases Inception Elaboration Construction Transition CSC 440: Software Engineering Slide #17 UP Schedule development cycle iteration phase inc. elaboration construction transition milestone release increment final production release An iteration end- A stable executable The difference point when some subset of the final (delta) between the At this point, the significant decision product. The end of releases of 2 system is released or evaluation occurs. each iteration is a subsequent for production use. minor release. iterations. CSC 440: Software Engineering Slide #18 Inception Phase Entry Criteria Need for project: original vision, legacy system, mock-up Activities Formulate scope of project Develop risk mitigation strategy Develop initial project plan with cost/schedule tradeoffs Prepare project environment Exit Criteria Product vision, containing core requirements Success criteria Initial risk assessment Estimate of required resources for elaboration phase CSC 440: Software Engineering Slide #19 Elaboration Phase Entry Criteria Exit criteria artifacts from last iteration Plan approved by project management and funding authority Required resources allocated Activities Define the core architecture Validate the architecture Baseline the architecture, addressing high risk items Refine requirements Exit Criteria Construction Phase plan, with number and contents of each iteration Development environment and tools Domain analysis model Executable architecture baseline CSC 440: Software Engineering Slide #20 Construction Phase Entry Criteria Exit criteria artifacts and products from last iteration Risks being mitigated during this iteration Defects being fixed during this iteration Activities Develop and test software components to satisfy use cases and nonfunctional requirements Manage resources and control process Assess the iteration Exit Criteria Updated versions of artifacts Iterative implementation of remaining lower risk elements Test cases and test results for iteration’s products Iteration plan for next iteration Measurable evaluation criteria for assessing next iteration’s results CSC 440: Software Engineering Slide #21 Transition Phase Entry Criteria Exit criteria artifacts from last iteration A software product mature enough to beta test Activities Test software product in customer environment Fine tune product based on customer feedback Deliver final product to customer Finalize end-user support documents Exit Criteria Update of previous documents as necessary “Post-mortem” analysis of project relative to original and revised success criteria CSC 440: Software Engineering Slide #22 UP Disciplines Discipline: set of activities and artifacts in one subject area Requirements: requirements analysis, including writing use cases and identifying non-functional requirements Design: software architecture, responsibility assignment to objects, database design, etc. Implementation: programming and building the system Test: unit tests for individual classes, integration tests for putting classes together, and acceptance tests by customers Environment: setting up tool and process environment for software development CSC 440: Software Engineering Slide #23 Disciplines across Iterations A four-week iteration (for example). A mini-project that includes work in most Note that disciplines, ending in a stable executable. although an iteration includes work in most Sample disciplines, the UP Disciplines relative effort and emphasis change Business Modeling over time. Focus of this Requirements This example is book suggestive, not Design literal. Implementation Test Deployment Configuration & Change Management Project Management Environment Iterations CSC 440: Software Engineering Slide #24 UP Variants Agile Unified Process (AUP) Lightweight variant Succeeded by Disciplined Agile Delivery (DAD) Open Unified Process (OpenUP) Used to develop Eclipse Framework Oracle Unified Method (OUM) Oracle development process Rational Unified Process (RUP) IBM/Rational software development process CSC 440: Software Engineering Slide #25 Object-Oriented Analysis & Design Analysis Investigation of the problem and requirements, with an emphasis on finding and describing the objects (or concepts) in the problem domain ex: a library information system would include domain objects like Book, Library, or Patron Design Creating a conceptual solution that fulfills the requirements by defining software objects and how they collaborate to fulfill the requirements ex: the Book object may have a title attribute and getChapter method CSC 440: Software Engineering Slide #26 Object-Oriented Analysis & Design Requirements Analysis Before OOA/D, write use cases to capture requirements Assigning Responsibilities The most important skill in OOA/D is assigning responsibilities to objects Design Patterns Named problem-solution formulas that codify best practices for object-oriented design UML Standard diagramming notation